The invention is particularly well suited for use in a rotary hearth pyrolyzer which has an annular hood and chamber in which an annular hearth rotates in a horizontal plane about the fixed center axis of the hood. Solid or semi-solid waste material dumped onto the rotary hearth, is, at present, distributed over the rotary hearth by means of a cylindrical spreader roll which extends transversely across the hearth. A scraper blade is provided on the downstream side of the spreader roll, relative to the directional movement of the rotary hearth, to remove solid waste material which sticks to the roll.
It can be appreciated by those skilled in the art that the inner and outer peripheries of the rotary hearth move at different speeds, because of the variance in their circumferential lengths. A cylindrical roll is simply not capable of accommodating this differential in speeds, thereby creating nonuniformity of the thickness of material being spread on the hearth. The invention is directed to the provision of a highly improved spreader roll and scraper blade assembly for producing a more uniformly thick bed of solid waste material on the rotary hearth.
Briefly stated, the invention is in a pyrolyzer having an annular hood and chamber in which is disposed an annular hearth which is mounted for rotation in a horizontal plane about a fixed, vertical axis. The annular hearth has inner and outer circular marginal edges or peripheries which rotate at different speeds, depending on the radial distances they are spaced from each other and the vertical axis about which the hearth rotates. A conically tapered spreader roll is disposed in the chamber immediately downstream from the inlet through which solid waste material is fed onto the rotary hearth for distributing the material evenly on the hearth. The tapered spreader roll extends transversely across the hearth and is conically tapered in decreasing circumferential length in a direction of the rotational axis of the hearth. The taper of the spreader roll is such that at any point measured longitudinally of the roll, the linear speed of the roll at such point equals the linear speed of the hearth at a point on the hearth opposite such point on the roll.
A scraper blade is disposed downstream of the tapered spreader roll in angular relation to the hearth and has a pair of opposing marginal edges, one of which edges engages the downstream side of the roll to remove solid waste material sticking thereto, and the other of which marginal edges terminates in parallel relation from the hearth to evenly distribute waste material on the hearth. Thus, both the scraper and roll coact to produce a more uniform supply of solid waste material on the hearth.